Improving the corrosion protection of 2524-T3-Al alloy through reactive sputtering Nb2O5 coatings

Abstract

This study focuses on the surface modification of 2524-T3 Al alloy substrates, highly prospective in aeronautical sector, by niobium oxide films employing reactive sputtering technique. A set of Nb2O5 thin films was obtained and characterized by various techniques including AFM, SEM, EDX, FTIR and XPS. After the morphological and structural characterization of the thin films, electrochemical and micro-abrasive wear tests were performed. The results of FTIR are not conclusive regarding the possible valences in the chemical structure of the thin film, such as Nb2O5 or NbO2, whereas XPS results only indicate the presence of Nb2O5. The EIS spectra indicate that both the bare alloy and the Nb2O5 covered material were suffering pitting corrosion, although the obtained parameters indicate that the coating is expected to increase the corrosion resistance of the material, reducing the severity of the pitting attack. Localised tests demonstrated that Nb2O5 coating was able to delay the onset of corrosion process and significantly improve corrosion resistance of alloy 2524-T3 Al alloy. The 2524-T3 Al alloy containing the Nb2O5 coating presented greater wear resistance than bare material, with reduction in the wear rate, under a mixed wear mode by rolling and scratching in both materials.